The general objective will be to gain a greater understanding of immune responses by studying less complex model systems than ourselves. During the past three years I have been visualizing erythrocyte responses in representatives of three groups of Amphibia (Triturus viridescens, Xenopus laevis, and Rana pipiens) which demonstrate different levels (functional, developmental, and anatomical) of sophistication in immunity. By using immunocytoadherence, in conjunction with carrier-hapten immunization, microtiter hemagglutination and immunofluorescence, I am proposing to explore a variety of aspects which relate to cooperative immunity in primitive vertebrates, e.g., (1) the specificity of immunized cells in embryos and adults possessing relatively small numbers of active cells, (2) the development of cells in embryos with specific capacities to produce antibody to different antigens, (3) the origin(s) of the "B" cell equivalent in vertebrates which do not use bone marrow as a hematopoietic site, (4) thymic dependence as it relates to "helper" activity, and (5-6) the cellular bases for short and long term immunologic memory and unresponsiveness in these humoral responses. My studies will involve in vivo and in vitro immunization.